Electrophotographic imaging member having two charge transport layers for limiting toner consumption

Abstract

An electrophotographic imaging member including a supporting substrate, an optional charge blocking layer, an optional adhesive layer, a charge generating layer, and a charge transporting element including two sequentially deposited charge transport layers each including a hole transport material and an optional film forming binder. A first charge transport layer exhibits a first charge carrier transit time and second charge transport layer exhibits a second charge carrier transit time. The two charge transport layers are formed in one of two ways. First, each layer can be formed from a different charge transport material so that the charge mobility of the charge transport material of the first charge transport layer is about 4 to about 20 times lower than the charge mobility of the charge transport material of the second charge transport layer. Or, alternatively, each charge transport layer can be made using a different amount of the same charge transport material. In this case, the first charge transport layer includes of an amount of charge transport material that is about 5% to about 30% less than an amount of charge transport material used to form the second charge transport layer. In either case, the resulting electrophotographic imaging member exhibits a discharge surface potential at a light exposure greater than about 3 erg/cm , at a post exposure delay between about 20 milliseconds and about 500 milliseconds that can be raised from about 20 to about 200 volts above a discharge potential of an imaging member having the same components as the imaging member of the present invention except having only a single charge transport layer with a thickness that is equivalent to the charge transporting element of the present invention.